Gauge Baryon Number and Dibaryonic Dark Matter

The minimal standard model of quarks and leptons is extended with a set of vectorlike fermions to allow baryon number $B$ to become a gauged $U(1)_B$ symmetry. The $B$ assignments of the new particles are determined by renormalizable interactions with the known quarks through a color triplet scalar diquark. The spontaneous breaking of $U(1)_B$ by a scalar with $B=3$ results in a conserved residual global $B$ symmetry. A singlet neutral scalar with $B=2$ is a possible long-lived dark-matter candidate.